Last summer, to great fanfare, the high school that my husband teaches at unveiled its new artificial turf field. Installed at considerable cost, that field was lauded as yet one more way that the school was working to protect the safety of its students.
As compared with a natural grass field (with all of its inherent unevenness, divots, rocks and gopher holes), an artificial turf field greatly reduces the number of sports-related injuries. One study of high school football players, for example, found that the number of concussions, ligament tears, muscle strains and ankle sprains was cut in half when players practiced and competed on artificial turf.
So important are these safety concerns that many schools will no longer allow their players to compete on a natural grass field. Those school districts that lack artificial turf fields may be excluded from league play or may be forced to rent such facilities in order to host local competitions.
However, recent reports aired on ESPN, NBC, and other networks have raised questions about the long-term safety of playing on artificial turf. Specifically, an increasing number of players and coaches, along with consumer safety advocates and environmental activists, are worried that those fields may be associated with an increased risk of cancer.
This is because artificial turf fields aren’t just made of plastic blades of grass. While those plastic blades are important to provide a natural grass look and feel, it is the rubber infill that is the most important aspect of an artificial turf field. That infill, usually made of black crumb rubber, is what provides the cushioning and traction necessary to ensure that soccer balls bounce and football cleats grab just as they would on a natural grass field. That same cushioning is also what helps reduce the frequency and severity of sports-related injuries.
The black crumb rubber used as infill is often made from recycled car tires. Among the 250 different chemicals that make up car tires are a number of compounds (including arsenic, benzene, cadmium and nickel) that are considered to be carcinogenic by organizations like the US Environmental Protection Agency (EPA) and the International Agency for Cancer Research.
When a soccer goalie dives onto the artificial turf to make a save, they may absorb small amounts of these cancer-causing chemicals through their skin. When a defensive lineman practices on a hot summer day, they may inhale small quantities of these carcinogenic compounds that are being released as gas. This is where the concern lies. Despite the fact that the amount of arsenic, benzene, cadmium and nickel in black crumb rubber is extremely low – well below the levels considered dangerous by regulatory agencies like the Consumer Product Safety Commission and the EPA – little is yet known about the risks associated with long-term low-level exposure, particularly for kids.
In fact, many advocates and activists are convinced that exposure to black crumb rubber is associated with a supposed increase in the number of lymphomas among athletes in the US. University of Washington coach Amy Griffin, for example, has a list of over 150 former collegiate and professional soccer players who were diagnosed with cancer after years of practicing and competing on artificial fields.
But before we rush to ban synthetic turf and replace existing artificial fields with natural grass, it’s important to recognize that anecdotal data like Ms. Griffin’s does not prove that there is a link between black crumb rubber and cancer. Self-reported disease clusters like these can help identify unexpected exposures or risks, but more often than not they turn out to be red herrings. Of nearly 600 such cancer clusters identified in the past 25 years, only three of these turned out to real upon further investigation. In less than 1% of such cases was a direct link between a cancer of concern and hypothesized environmental exposure demonstrated.
To date, more than 50 studies have looked at the health risks of crumb rubber. Not a single study has found a link between exposure to black crumb rubber and cancer. That does not mean that such a link does not exist, but we need studies that are carefully designed to look at these risks. For example, we need to collect the data that will allow us to compare rates of cancer among people who play soccer versus those who do not. Similarly, we need to collect the data that will allow us to compare rates of cancer among those that play soccer on artificial fields versus those that do not.
In fact, the state of California is doing just that. In the largest study of its kind, the California Office of Environmental Health Hazard Assessment is analyzing the different type chemicals released from new, uninstalled and in-use artificial fields, monitoring the air above such fields and playgrounds for specific chemicals that can be inhaled, and estimating oral and dermal exposures associated with playing on artificial turf. They will also be monitoring personal exposure to various carcinogens of athletes who play on synthetic turf. The results of that three-year $2.9 million study should be available in 2018.
Until then, we really won’t know whether or not these fields are 100% safe. The bulk of current data suggest that they are, but that is little comfort for the millions of concerned parents whose children play on those fields every day. Will they continue to take the risk or, given the stakes, will they opt to protect their children despite the lack of definitive evidence?
[This blog entry was originally presented as an oral commentary on Northeast Public Radio on February 25, 2016, and is available on the WAMC website.]